Intracranial arachnoid cyst; an unusual cause of epiphora

Insular operculum disconnection and herniation into the parapharyngeal space due to a fetal Galassi Type III arachnoid cyst: a case report

Arachnoid cysts (ACs) are frequently encountered as incidental findings in the brain, with most cases being asymptomatic and not requiring intervention. However, severe brain malformations caused by ACs are rare. In this study, we describe the case of an 8-day-old female infant with a left mandibular mass that was diagnosed as an insular operculum, which has become disconnected and herniated into the parapharyngeal space through an incompletely ossified greater wing of the sphenoid, caused by a fetal Galassi Type III AC. The newborn also exhibited left hearing impairment, which did not improve at the 6-month follow-up after the cyst peritoneal shunt. This report highlights that ACs that manifest during the early fetal period may protrude from the cranial cavity through an unossified skull, potentially affecting the development of brain tissues.

Pneumosinus Dilatans: An exploration into the association between Arachnoid Cyst, Meningioma and the pathogenesis of Pneumosinus Dilatans

OBJECTIVES

To investigate the association between certain intracranial masses (meningioma and arachnoid cyst) and the incidence of Pneumosinus Dilatans (PSD) - including whether the size of the mass correlates with severity of the condition.

PATIENTS AND METHODS

A review of the available case reports on PSD was performed. Clinical data was extracted from 111 case reports for analysis. A further case-control study was performed using CT Head datasets to investigate the aetiological relationship between intracranial masses and PSD. Cases included patients with confirmed arachnoid cyst or meningioma. Controls included patients with no intracranial masses.

RESULTS

PSD is most common in the frontal (48%) and sphenoid sinuses (43%). Men are twice as likely to be affected as women. 58% of cases occur in patients aged 35 or under. The most common symptoms reported are facial deformities (39%), headache (24%) and visual loss (15%). Unexplained visual changes (e.g. diplopia, reduced visual acuity) are strongly correlated with sphenoid sinus involvement. PSD is more common in patients with skull-base meningioma (OR 5.67) and middle cranial fossa arachnoid cysts (OR 10.00). Mean sinus volume in patients with PSD can increase by up to 4 times.

CONCLUSION

We present the first direct investigation into the relationship between meningioma, arachnoid cyst and Pneumosinus Dilatans. There is a statistical correlation between skull-base meningioma and middle cranial fossa arachnoid cysts and the incidence of PSD. This specific anatomical relation suggests that local factors contribute to the pathogenesis of the condition. Alterations in intracranial pressure due to mass effect or vascular occlusion, in addition to the localised release of bone growth factors (IGF-1, IGF-2, PDGF), are possible mechanisms for this. The first peak in incidence of PSD coincides with the completion of normal sinus pneumatisation, which raises the further possibility that predisposing genetic factors also contribute.